Position



y 1954 E. J. WEBER 3,142,782

TRANSISTOR SYSTEM FOR GAS IGNITION AND THE LIKE Filed Nov. 28, 1962 Qfl' CONTACT FULL ON POSITION POSITION POSITION INVENTORZ 8v EARL J. WEBER United States Patent 3,142,782 TRANSISTOR SYSTEM FOR GAS IGNITION AND TEE LIKE Earl J. Weber, Bay Viilage, Ohio, assignor to American Gas Association, Incorporated, New York, N.Y., a

corporation of New York Filed Nov. 28, 1962, Ser. No. 240,510 9 Claims. (Cl. 31786) The invention relates to transistor circuits for producing oscillations during controlled time" intervals, and to systems using such circuits to provide spark discharges suitable for igniting a gas such as is used in the ordinary gas burner of a cooking range or space heater. In another aspect the invention relates to improvements in gas burner systems of the class in which ignition is produced by a transistor-controlled electrical spark discharge.

In gas burning systems it is generally important that gas emanating from the burner be ignited soon after it is first turned on. One of the common ways to provide such ignition in the past has been by means of a pilot gas burner. However, for many purposes it is considered desirable to eliminate the gas pilot all together, replacing it with an electrical ignition system. Such a replacement eliminates unnecessary heat loss to the surrounding environment, unnecessary fuel consumption and potential hazard to person and property inherent in use of a pilot gas flame. Furthermore, the use of electrical ignition offers the possibility of quicker, more reliable and more flexible ignition systems.

However, certain additional problems arise when electrical ignition is applied to gas burners. First, if electrical current for operating the ignition system is supplied from the usual line power source, it must be anticipated that the supply of current will be occasionally interrupted by power failures, sometimes for many hours or even for several days. Unless some special provision is made the gas burner ignition system will be inoperative during such periods of power failure. If, to overcome this problem, a special local battery is used to operate the electrical igniter, it then becomes important from practical considerations to employ an arrangement permitting the use of a battery which is as small as possible and which does not require frequent replacement, which in turn requires an electrical ignition system using as little current as possible, on the average. To minimize the current requirements the igniter should be utilized for as short periods of time as possible. Furthermore, for greatest flexibility and eificiency it is often important that the ignition system be capable of rapid and reliable switching on and off of the ignition action, without requiring for this purpose expensive and often troublesome high-current or high-voltage switches, despite the fact that the spark discharge is itself inherently a high-current and high-voltage phenomenon. In addition, from the viewpoints of minimizing space requirements, expense, and current demand it is obviously desirable to utilize as simple an arrangement as possible.

Accordingly it is an object of my invention to provide a new and improved electrical ignition system for gas burners.

Another object is to provide such an ignition system which is all-electronic, requiring no pilot flame at all.

A further object is to provide such an ignition system which is capable of continued satisfactory operation for relatively long periods during electrical power line failures.

It is a further object to provide such a system which does not require a large supply battery or frequent battery replacement.

Still another object is to provide an all-electronic gas ignition system in which the igniter is operated only for brief periods in normal operation.

Another object is to provide a spark-discharge ignition system for gas burners which is simple, small in size, efficient in operation, reliable in performance, flexible in applicationand yet relatively inexpensive in both original and maintenance costs.

It is also an object to provide a new and improved transistor-operated spark-discharge system for producing a spark discharge for a predetermined time interval following the closing of a switch.

These and other objects of the invention are achieved by utilizing a transistor oscillator circuit supplying oscillations to a spark coil or similar voltage-multiplying device Which is connected in turn to an igniter typically comprising a pair of spark-discharge electrodes disposed adjacent the burner for which ignition is to be provided. When the oscillator is operating, a spark discharge is produced between the electrodes of the igniter in such intensity and position as to provide ignition of the gas emanating from the burner. However normally the oscillator is non-operative because of the D.C.-blocking action of a capacitor connected between the bias supply means for the transistor and an operating electrode of the transistor. Provision is made for controllably rendering the transistor oscillator operative whenever the gas control for the burner to be ignited is turned on. Furthermore, means are provided for automatically rendering the oscillator again non-operative, thereby terminating the ignition discharge, after a predetermined relatively short interval suflicient to produce the desired ignition.

The means for rendering the transistor oscillator operative to produce an ignition discharge comprise a timing-control transistor having its emitter-to-collector current path connected in parallel with the bias-blocking capacitor in the transistor oscillator circuit, and switch means actuated by adjustment of the gas control means through a predetermined condition for which suflicient gas emanates from the burner to support ignition; such actuation of the switch means causes the timing-control transistor to become strongly conductive and thereby short-circuits the blocking capacitor to provide the oscillator transistor with the necessary operating bias. A timing capacitor connected between the base and collector electrodes of the timing-control transistor then maintains the timing-control transistor conductive for the desired predetermined ignition interval, and charges during said interval to a point at which the timing-control transistor becomes non-conductive to arrest the oscillations and the ignition spark discharge.

With this system a number of gas control means may be connected in parallel so that any one of them will operate the switch means to produce ignition, regardless of whether the other gas control means are turned on or off, and a corresponding number of burners and a plurality of igniters may be associated with the voltage-multiplying device, the supply of gas for each of the burners being controlled by a corresponding one of the gas control means. In this way, turning-on of any of the gas control means for any one of the burners will actuate the switch means to render operative the transistor oscillator circuit and to provide a spark discharge for igniting the corresponding burner. The oscillator will continue to operate, and the spark discharge will persist, for a preselected interval suitable for assuring gas ignition. However, the oscillator and ignition system become non-operative, immediately after this interval following each turning-on of the gas control.

Preferably the current necessary for operation of my ignition system is provided by a small, relatively lowvoltage and low-storage-capacity, rechargeable battery connected to the power line by a simple rectifying circuit acting as a trickle charger normally to maintain the battery charged and to recharge it following power failures.

From the foregoing it will be apparent that my system is all-electronic and requires no pilot flame whatsoever. The hazard of temporary power failures is overcome by the use of a battery which will continue to supply the necessary operating current for relatively long periods of time even if the power fails. Use of a small, inexpensive and readily replaceable battery is made possible by the low battery drain inherent in my system, provided especially by the fact that the igniter operation is terminated immediately after the interval required for ignition and current is drawn by the system only during the relatively brief periods immediately following actuation of the switch means. The current drain is also maintained low because of the extreme simplicity of the circuit and the absence of the requirement for any current-operated switches or like devices. The system is inherently highly reliable, flexible and fast-acting so as to permit rapid consecutive ignition of a number of burners by their related gas controls.

A particularly effective yet simple transistor circuit arrangement for accomplishing the above objectives in accordance with the invention comprises coil means having an input circuit connected between the emitter and collector electrodes of a first transistor, having a feedback circuit for supplying signals to the base of said first transistor to produce a regenerative effect inducing electrical oscillations when appropriate biases are applied to said transistor, and having an output circuit for deriving voltage-multiplied signals from said input circuit and for applying them to the spark-discharge electrodes. A smalls'torage-capacity rechargeable battery'serving as the bias supply for the first transistor is connected in series with emitter electrode of the transistor, and a first capacitor in series with the feedback Winding between the base electrode of the first transistor and the end of the supply battery remote from the emitter electrode normally prevents application of operating bias to the base electrode. A second transistor isdisposed with its emitter-collector path in shunt with the first capacitor, and has its base electrode connected to a source of reference potential Which is effectively isolated from its collector electrode under normal conditions. .More particularly, the collector of the second transistor is directly connected to the side of the first capacitor which connects with the feedback winding. The collector of the latter transistor is also connected through a second capacitor to the base electrode of the second transistor. A momentary-contact, single-pole, single-throw switch is connected between the collector electrode of the secondtra'nsistor and the source of reference potential, and is linked to the gas control means for one of the burners in such a manner that when the gas control is turned on by a slight amount this switch is closed. This connects the collector of the second transistor to the source of reference potential, discharging both the first and the second capacitors, and establishes conduction through the emitter-collector current path of the second transistor whereby bias is applied to the first transistor and oscillations and ignition sparks are produced.

Even though the momentary-contact switch quickly passes through its closed condition'in the normal turningon of the gas control, the potential of the collector of the second transistor does not immediately revert to its normal value because of the time required to charge the second capacitor. Accordingly oscillations and ignition discharge continue until the second capacitor has charged to the point'where the second transistor becomes nonconductive, rendering the first transistor also non-conductive, terminating the oscillations and the ignition dis- 5 charge. The time duration during which oscillations continue is increased by making the value of the second capacitor larger, and may be adjusted to any suitable value. Preferably this time duration is only sufficient to assure proper ignition.

Connected across the rechargeable battery in a preferred form of the invention is a line-connected step-down transformer and a suitable diode rectifier and current-limiting resistor for normally applying direct voltage across the battery in the direction to recharge it. The primary of the line-connected transformer is connected to the alternating current power line. Because very little power is consumed by the circuit and only a very small amount of current is necessary normally to maintain the battery charged, in the event of a power failure the small-storagecapacity battery is capable of providing ignition for several days, for example, hence long enough to accommodate any normally-encountered interruptions of power service. This specific embodiment of the invention is especially adapted to accomplish the above-mentioned objects including simplicity, inexpensiveness, reliability, fast action and protection against power failure which are desired in such a system.

Other objects and features of the invention will become apparent from a consideration of the following detailed description of the invention taken in connection with the accompanying drawing, in which the single figure is a schematic representation illustrating a preferred embodiment of the invention.

Referring now specifically to the form of the invention illustrated in the figure, the invention will first be described with specific reference to a preferred embodiment suitable for inclusion in a four-burner gas cooking range, although it will be apparent to one skilled in the art that is is equally applicable to use with fewer or with more burners, with burners designed for other uses such as space heating, and with gases other than ordinary cooking gas.

As indicated in the drawing, the gas burners 10, 12, 14 and 16 are supplied with fuel-gas by means of inlet pipes A, B, C and D respectively at rates determined by the adjustment of gas controls 18, 20, 22 and 24 respectively. It will be understood that outlet pipes A1, B1, C1, and D1 of gas controls 18, 20, 22 and 24, respectively are connected by appropriate piping to the burner inlet pipes A, B, C and D respectively. Inlet pipes A2, B2, C2 and D2 supply gas to the controls 18, 20, 22 and 24, respectively, from the main gas supply. The gas'controls are ordinary rotary gas valves each of which is in its off condition when its handle such as 26 is in the vertical position as shown for control 18, is fully on when its handle is turned clockwise to a horizontal position as shown from control 22, and provides gradually increasing gas flow as its handle is turned from the off to the fully on posi tion.

The foregoing portions of the system represent an entirely conventional arrangement of piping, controls, and burners for a gas range and hence need not be described in detail.

Associated with the gas controls 18, 20, 22 and 24 are Wiper-type switch arms 28, 30, 32 and 34 respectively. Each of these arms is aflixed to its associated gas control so as to rotate with its corresponding handle, and each is at all times grounded as by a continuous Sliding contact between the switch arm and a grounded metallic support shaft of the rotary gas control or merely by a short ground wire connected to each switch arm and of suflicient length to accommodate the rotary motion thereof. Mounted in fixed position adjacent each of the four gas controls are interconnected electrical contacts 36, 38, 39 and 40 positioned to be contacted momentarily by switch arms 28, 36, 32 and 34 respectively at a predetermined point in the rotary motion of the associated gas control handle. More particularly, each of these fixed contacts is positioned so that it is normally insulated from its switch arm, as illustrated in the case of controls 18, 22

and 24. However, each fixed contact makes electrical connection to its associated wiper arm whenever its gas control has been rotated from its oil position toward its fully on position by an amount which provides sufficient gas to the associated burner to maintain an adequate flame for reliable ignition, as illustrated by the position shown for control 26. Accordingly, whenever any one of the gas controls is turned on to a usable operating position its associated switch arm wipes across its fixed contact and momentarily grounds its associated fixed contact. It is this grounding which is utilized to initiate ignition of that burner which is supplied with gas by the control which is turned on, in a manner now to be described.

Adjacent and operatively associated with gas burners 10, 12, 14 and 16 are separate gas ignition means or igniters comprising the pairs of spark discharge electrodes 41, 42, 44 and 46 respectively. Each of these pairs of electrodes is disposed in relation to the orifices of the corresponding burner from which gas emanates so that a spark discharge between the members of the pair of electrodes will provide ignition of the emanating gas. Such a spark discharge occurs whenever the voltage applied between the two electrodes is sufiiciently high. It will be understood that appropriate flash tubes may be provided between each spark gap and its associated burner, that one set of electrodes may be used to ignite more than one burner, and that one of the electrodes of each pair may comprise a flash-tube or part of a burner.

The requisite high voltage for operating the sparkdischarge electrodes is provided by a transistor oscillator and associated voltage-multiplyng transformer, in this case a spark coil. The transistor oscillator comprises a transistor 50, in this example a PNP-type transistor, having conventional emitter, collector and base electrodes as shown schematically, and having connected in series between its emitter and collector electrodes a bias supply battery 52 and primary coil means comprising four series-connected transformer primaries 54, 56, 58 and 60. An additional feed-back coil 62 is connected between the battery-connected end of coil 60 and the base electrode of transistor 50, and is inductively coupled to primary coil 60 in such phase relation as to provide regenerative feed-back to the base of transistor Si) by way of series capacitor 64. Inductively coupled to primary coils 54, 56, 58 and 60 respectively are secondary coils 66, 68, 70 and 72, the ratio of secondary to primary turns and the arrangement of the windings being such as to produce a large voltage-multiplying effect as is typical in spark coils of known types. Spark coils of the general class used in model airplanes are suitable for this purpose.

Assuming that battery 52 is initially adequately charged and connected as shown with its positive terminal connected to the emitter of transistor 54}, and further assuming that capacitor 64- is short-circuited so that bias from battery 52 can reach the base electrode of transistor 5%, the portion of the circuit thus far described Will operate as a simple but eifective electrical oscillator producing recurrent current pulses through the primary coils 54, 56, 58 and 60. These pulses produce high-voltage pulses in the secondary coils by usual transformer action, which are applied to the pairs of ignition electrodes 41, 42, 44 and 46 in sufiicient intensity to produce a spark discharge between the members of each pair of electrodes and to produce ignition of gas emanating from any of the burners. However, capacitor 64 is normally not shortcircuited but, on the contrary, blocks the application of current from bias battery 52 to the base electrode of transistor 50 so that the above-described oscillation and ignition conditions are inhibited.

The short-circuiting of the capacitor 64 required to render the oscillator operative and to produce ignition sparks is initiated by the turning-on of any one of the burner controls 18, 20, 22 and 24, which momentarily grounds fixed contacts 36, 38, 39 and 40 through the asso ciated switch arm of the gas control which is operated. A second transistor 70, which is herein termed a timingcontrol transistor since it is used to control the time of actuation of the transistor oscillator, has its emitter connected to the base of transistor 50 and its collector connected to the end of the feed-back coil 62 remote from battery 52. Transistor 70 is a PNP-type transistor in this example. With this arrangement the emitter-tocollector current path of transistor 70 is directly in shunt with the bias-blocking capacitor 64. The base of transistor 70 is grounded while its emitter and collector are eflectively floating in potential with respect to the base, and accordingly transistor 70 normally presents a high resistance in its emitter-to-collector path and maintains the blocking action of capacitor 64 to prevent the application of operating bias to the base of the transistor 50. However, as soon as any one of fixed contacts 36, 38, 39 and is momentarily grounded during the turning on of any one of the gas controls 18, 20, 22 and 24, the connection 72 between the latter momentarily-grounded contacts and the collector of transistor 70 grounds the collector and renders transistor 70 conductive substantially immediately. A conductive path from bias supply 52 is thereby established to the base of the oscillator transistor by way of the emitter-to-collector path of transistor 70, so that the transistor oscillator becomes operative and produces a spark discharge to ignite that burner the control for which was turned on.

However, to assure adequate ignition it is important that the spark discharge continue for a substantial predetermined time intervalfor example, of the order of at least several secondswhereas the time interval during which the switch arm of any switch on the gas controls is closed during the turning on of the control is generally many times shorter than this required interval. Utilizing only the portion of the circuit thus far described, the oscillator would become inoperative again almost as soon as it was turned on by the passage of the switch arm past its associated contact. To overcome this difficulty and to provide for a predetermined substantial interval of spark discharge, a second capacitor 76 is connected directly be tween the base and collector electrodes of the timing-control transistor 70. This capacitor is discharged to ground during the momentary grounding of fixed contacts 36, 38, 39 and 4%] as one of the gas controls is turned on, and hence does not interfere with the above-described turning on of the transistor oscillator and the initiation of the spark discharge. However, after the switch arm of the operated gas control has been turned past its associated fixed contact to remove the grounding of the collector transistor 70, the voltage of the collector of transistor persists at its operating level as capacitor 76 is charged by current through transistor 70. When capacitor 76 has charged for a time interval characteristic of the value of capacitor 76 and the values of the particular circuit elements used in conjunction therewith, transistor 70 becomes non-conductive, the supply of operating bias to oscillator transistor 50 is interrupted, and spark ignition terminates.

Blocking capacitor 64 is ordinarily made of small capacity compared to the capacity of timing capicitor 76. It therefore charges relatively rapidly as transistor 70 be comes non-conductive, and does not materially affect the duration of the interval during which transistor 70 is conductive and ignition sparks are produced. Since the rate of charge of timing condensor 76 depends in a complex way upon the exact values of the various other electrical elements of the system, selection of the value of capacitor 76 to produce a desired ignition interval is preferably determined experimentally by observing the ignition interval produced by a given value of capacitor 76 and increasing or decreasing this value to increase or decrease this interval to the desired time period.

The frequency of the generated oscillations increases with the effective resistance between emitter and base of transistor 50. In the embodiment shown in the figure this resistance is the emitter-to-collector path of the transistor 70, and varies from a very low value to a very high value as capacitor 76 charges. This causes the frequency of oscillations to vary from a low value such as a few hundred cycles per second to a supersonic frequency for which energy insufiicient for ignition is transferred to the secondary of the spark coil. Accordingly in some cases there -may be an unduly long delay in the start-of oscillations and ignition due to the time required for the resistance of transistor 70 to build up to a value for which oscillationswill begin. In this event a resistor may be added in the base circuit of transistor St) to assure a minimum resistance adequate to provide sufiiciently prompt ignition.

To maintain bias battery 52 in an adequately-charged condition the secondary winding 89 of a voltage step-down transformer 82 is provided with one end directly connected to the negative side of battery 52 and the other end connected to the positive side of battery 52 by way of a rectifier84, such as a crystal diode, and a series current-limiting resistor 86, the rectifier being poled so that it conducts more strongly when the end of secondary 8t connected thereto is positive. The primary 88 of transformer 82 may be connected to an AC. line supply, typically of 110 .volts. This combination therefore constitutes a trickle charger of conventional form for storage battery 52, which may be a small nickel-cadmium storage cell. Because of the low current drain on battery 52, the line power required to maintain a charge thereon is extremely low, typically one watt or less, and should the line power fail the battery will be capable of providing continued operation for a relatively long period of the order of many hours or even a few days. If the line power available is direct current, then appropriate modifications which will readily be evident to one skilled in the art may be provided for directly applying a divided-down portion of the direct-current line voltage across the battery 52..

The figure illustrates a simple switch arrangement for initiating the spark discharge when a gas control is turned on, and which will also produce an unnecessary discharge as the control is turned oif. The latter discharge may be avoided by using a switch which provides momentary closing for one direction of motion only. It is also contemplated that the switch disclosed and claimed in the copending application Serial No. 167,723 of Fred Westberg, filed January 22, 1962, and entitled Switch Control Apparatus, Especially for Gas Burner Valves, maybe used for this purpose. In the latter case the momentary-contact part of the switch is connected as shown herein while the permanent contact portion of the switch is connected between battery 52 and the emitter of transistor 54 Without thereby limiting the scope of the invention, the following specific values of various elements suitable for use in the above-described embodiment of the invention are provided in the interest of complete definiteness:

Line supply voltage (A.C.) 110 volts. Discharge electrodes 41, 42,

44 and 46 No. 22 wire, gap. Capacitor 64 l microfarads, 6 volt D.C. Capacitor '76 500 microfarads, 6 volt Discharge electrode voltage Approximately 5000 volts.

With the foregoing values of components, actuation of the igniters in response to turning on of any ofthe control valves was produced for a period of the order of three seconds. The power supplied from the power line to maintain battery 52 charged was a fraction of a watt, and the system remained operative for at least two days after any removai of line power.

Accordingly, it will be appreciated that there has been provided an all-electronic ignition system forvfluid fuel burners which does not require the use of pilot flames, special burner valves or special tubing, filters or pilot valves; does not involve switching of high currents or high voltages; requires extremely small amounts of line power for normal operation yet remains operativefor long periods following interruption of line power and requires only a small, cheap and conveniently replaceable battery; provides an adequate interval for ignition of any burner which is turned on; operates extremely rapidly so as to permit rapid consecutive ignition of the various burners; and, due to the inherent buzzing sound associated with operation of the ignition electrodes, provides a convenient indication to the operator that proper operation is taking place.

In connection with the use of the above-describedignition system, it will be appreciated that since transistors have characteristics which change, and usually deteriorate, at highly elevated temperatures, it is generally desirable to arrange and to locate the transistors so that they are not unduly heated by the burners, as may readily be provided by strategic placement or suitable thermal insulation of the transistors, or both.

Although my ignition system is especially advantageous in forms using a line-connected trickle charger and a rechargeable battery, as shown in the figure, it is also highly advantageous in applications in-Which no trickle charger is used, or in which the bias supply'is not rechargeable.

While the invention has been described with particular reference to specific embodiments thereof, it will be understood that it may be embodied in many diverse forms without departing from the scope of the invention as defined by the appended claims.

I claim:

1. A gas ignition system, comprising:

gasburner means;

adjustable gas control meansfor supplying gas to said burner means;

igniter means responsive to voltage applied thereto to ignite gas emanating from said burner means;

a transistor oscillator circuit for applying voltage to said igniter when said oscillator circuit is operating, said circuit including a transistor, a source of operating bias for an operating elctrode of said transistor, and means normally preventing the application of said bias to said operating electrode to maintain said oscillator circuit normally non-operative;

means responsive to adjustment of said gas control means momentarily to supply operating bias to said operating electrode; and

reactive circuit means for maintaining the supply of operating bias to said operating electrode for a limited time interval following said adjustment of said gas control means, thereby to operate said igniter means for a preselected time interval following said adjustment.

2. A gas ignition system comprising:

a gas burner;

means for supplying gas to said burner;

adjustable gas control means associated with said gassupplying means for controlling the rate of flow of said gas to said burner;

a spark-discharge igniter having discharge means situated adjacent said burner to produce, upon the occurrence of a spark from said discharge means, ignition of gas emanating from said burner;

a transistor oscillator circuit connected to said igniter for producing sparks from said discharge means upon the occurrence of electrical oscillations in said circuit, said circuit including a first transistor, 2. source of operating bias for said first transistor, and first capacitive means disposed in series between said source of operating bias and one of the operating electrodes of said first transistor normally to prevent supply or" operating bias to said one operating electrode and normally to inhibit generation of oscillations in said circuit;

a normally non-conductive second transistor having its emitter-to-collector current path in parallel with said first capacitive means to supply operating bias to said one operating electrode when rendered conductive;

switch means responsive to adjustment of said gas control means through a predetermined condition thereof for supplying said second transistor with operating potentials to render it conductive while said switch means is in said predetermined condition; and

second capacitive means connected between the base and collector electrodes of said second transistor for maintaining said second transistor conductive for an interval of predetermined limited duration after said switch means has passed through said predetermined condition, whereby said first transistor is rendered conductive to produce oscillations in said circuit and sparks from said discharge means during said interval.

3. A system for producing sparks during a predetermined time interval for ignition of gas from a gas burner, comprising:

first and second transistors each having at least an emitter, a base, and a collector;

means for normally maintaining said transistors nonconductive;

coil means having an input circuit, an output circuit and a feed-back circuit;

means connecting said input circuit between said emitter and collector of said first transistor;

means connecting said emitter and collector of said second transistor, one to said feedback circuit and the other to said base of said first transistor;

a capacitor connected between said collector and said base of said second transistor;

means for momentarily discharging said capacitor when said gas is to be ignited;

means including a supply current source for producing a flow of current to charge said discharged capacitor and to render said second transistor conducting;

means for biasing said first transistor in its conductive state when said second transistor is rendered conducting, whereby oscillations are produced in said coil means to provide a high voltage in said output circuit; and

means connected to said output circuit and responsive to said high voltage for producing sparks;

said fiow of current decreasing as said capacitor charges until said second transistor is rendered nonconductive to non-conductively bias said first transistor for termination of said oscillations and said sparks.

4. Gas ignition apparatus, comprising:

a transistor oscillator circuit including a first transistor, first capacitive means, coil means, and operating bias supply means operatively associated with each other to produce electrical oscillations in said coil means when said first transistor is conductive, said first capacitive means being situated in series between said operating bias supply means and the base electrode of said first transistor normally to interrupt application of operating bias to said base electrode from said operating bias means, thereby to render said first transistor normally substantially non-conductive and said oscillator normally non-operative;

a gas igniter having a pair of spark-discharge electrodes and responsive to the occurrence of oscillations in said coil means to produce between said electrodes a spark discharge capable of igniting a gas;

a second transistor having its emitter-to-collector cur rent path in shunt with said first capacitive means and having associated therewith a collector-to-base circuit which is normally open for direct current, whereby said second transistor is rendered normally non-conductive between its emitter and collector electrodes to maintain said first transistor also in its normally non-conductive condition;

normally-open momentary-contact switch means connected between said base electrode and said collector electrode of said second transistor;

means for supplying to the vicinity of said igniter a gas to be ignited upon the occurrence of a spark discharge between said electrodes of said igniter, said gas supply means including gas control means adjustable to various conditions to produce different rates of flow of said gas through said gas supplying means;

means responsive to adjustment of said gas control means to a predetermined condition momentarily to close said switch means, thereby to render conductive both said second transistor and said first transistor and to produce a spark discharge between said electrodes of said igniter; and

second capacitive means connected between said collector electrode of said second transistor and said base electrode thereof for supplying current to said collector electrode of said second transistor for a predetermined interval after said momentary closing of said switch means in suificient quantity to maintain said oscillations and said discharge during said predetermined interval, after which said current, said oscillations and said discharge terminate.

5. A gas burner ignition system, comprising:

a gas burner;

gas control means adjustable to turn on and off the supply of gas to said burner;

spark-discharge means disposed adjacent said gas burner for igniting gas emanating from said burner;

a normally-quiescent transistor oscillator circuit connected to said spark-discharge means to produce a spark-discharge therefrom when said transistor oscillator is rendered active;

switch means momentarily actuatable in response to adjustment of said gas control means from its off to its on condition to render said transistor oscillator circuit momentarily active, thereby to produce a spark-discharge from said spark-discharge means;

a reactive element associated with said transistor oscillator circuit for maintaining said circuit active after actuation of said switch means for a time interval dependent upon the value of said element, thereby to maintain said spark-discharge for said interval;

a rechargeable battery for supplying operating biases for said transistor oscillator circuit; and

means responsive to power-line voltage for applying a direct charging current to said battery.

6. The system of claim 5, in which said transistor oscillator circuit comprises a first transistor, a normally-open direct-current path situated between the emitter and base electrodes of said first transistor and in series with said battery for normally preventing application of operating bias to said first transistor, a normally non-conductive second transistor having its emitter-to-collector current path connected to close said normally-open direct-current path when said second transistor is rendered conductive, and means responsive to actuation of said switch means to render said second transistor conductive.

7. The system of claim 6 in which said reactive element comprises a capacitor connected between the collector and base electrodes of said second transistor and in which H 12 said switch means is responsive to actuation thereof to transistor oscillator circuit includes voltage-multiplying h ti it id itor, transformer means for supplying oscillations to said spark- 8. The systemof claim 7, in which said switch means discharge means comprises a switch having a wiper arm and another R f contact, said switch being responsive to adjustment of said e erences Cited m file of Patent gas control means through apredetermined position, for UNITED STATES .PATENTS which gas sufiicient for.ignition emanates from sa d 2,479,797 Wasser Aug. 23, 1949 burner, to wipe'said. arm over said contact. 2,733,759 McCammant 'Feb. 7, 1956 9. A system in accordance with claim 7, inwhich Said 2,869,633 Schaaf et a1. Jan. 20, 1959 

1. A GAS IGNITION SYSTEM, COMPRISING: GAS BURNER MEANS; ADJUSTABLE GAS CONTROL MEANS FOR SUPPLYING GAS TO SAID BURNER MEANS; IGNITER MEANS RESPONSIVE TO VOLTAGE APPLIED THERETO TO IGNITE GAS EMANATING FROM SAID BURNER MEANS; A TRANSISTOR OSCILLATOR CIRCUIT FOR APPLYING VOLTAGE TO SAID IGNITER WHEN SAID OSCILLATOR CIRCUIT IS OPERATING, SAID CIRCUIT INCLUDING A TRANSISTOR, A SOURCE OF OPERATING BIAS FOR AN OPERATING ELECTRODE OF SAID TRANSISTOR, AND MEANS NORMALLY PREVENTING THE APPLICATION OF SAID BIAS TO SAID OPERATING ELECTRODE TO MAINTAIN SAID OSCILLATOR CIRCUIT NORMALLY NON-OPERATIVE; MEANS RESPONSIVE TO ADJUSTMENT OF SAID GAS CONTROL MEANS MOMENTARILY TO SUPPLY OPERATING BIAS TO SAID OPERATING ELECTRODE; AND REACTIVE CIRCUIT MEANS FOR MAINTAINING THE SUPPLY OF OPERATING BIAS TO SAID OPERATING ELECTRODE FOR A LIMITED TIME INTERVAL FOLLOWING SAID ADJUSTMENT OF SAID GAS CONTROL MEANS, THEREBY TO OPERATE SAID IGNITER MEANS FOR A PRESELECTED TIME INTERVAL FOLLOWING SAID ADJUSTMENT. 